Hello!
In reference to the manual the I/O pins are typically 5V tolerant. The footnotes for Table 4, specify the different configurations for different pins in the LPC546XX datasheet. In addition you can refer to page 83 of the same document for the limiting values on the pins. It is always recommended to work slightly below the limits.
For specific pin configurations which can allow for 5V, please refer to the LPC546XX datasheet:
https://www.nxp.com/docs/en/data-sheet/LPC546XX.pdf
For general information regarding these pins functions, refer to the LPC546XX manual:
https://www.nxp.com/webapp/Download?colCode=UM10912
Hope this helps!